Electronic structures of Bi4-xLaxTi3O12 and Bi4ZrxTi3-xO12 single crystals studied by soft-X-ray spectroscopy

The electronic structures of La-doped Bi4Ti3O12 (Bi4-xLaxTi3O12) and Zr-doped Bi4Ti3O12 (Bi4ZrxTi3-xO12) single crystals have been studied by X-ray absorption spectroscopy (XAS) and soft-X-ray emission spectroscopy (SXES). In both Bi4-xLaxTi3O12 and Bi4Ti3-xZrxO12, the Ti 3d and O 2p partial densities of states (PDOS) in the valence band region were observed in O 1s and Ti 2p SXES spectra. The energy position of the Ti 3d state overlapped with that of the O 2p state, indicating the occurrence of the hybridization effect between the Ti 3d and O 2p states. The hybridization effect of Bi4-xLaxTi3O12 increases with, increasing La dopant concentration, although that of Bi4Ti3-xZrxO12 does not depends on Zr dopant concentration. This finding indicates that the hybridization effect is closely related to the change in,the bond length between Ti and O ions.